FZJ Fermi Chopper OPI: Disable start button when interlock bad

[davidkeymer]

Issue Description

As a technician responsible for the FZJ ("Jülich") fermi chopper systems, I would like to prevent the chopper from being started when an interlock signal is 'bad' e.g. the vacuum has tripped.

How & Where?

Discovered by technicians working on MARI, but believed to be present on the other FZJ systems on MERLIN and MAPS.

Reproducible (Yes/No)?

Yes - press start button on chopper OPI when interlock bad (shown by red LED on advanced tab).

Additional Information

• workaround/fix to be put in OPI initially, due to requirement that it is present for the upcoming cycle
• suggest use rule in OPI to monitor interlock PV and disable button accordingly
• logic could be transferred to IOC in long-term, after further discussions with technicians

_{See our Git Workflow.}

Acceptance Criteria

• Start button can no longer be pressed (greyed-out and disabled) when interlock signal is bad
• OPI is patched onto relevant instruments i.e. MARI, MERLIN, MAPS

How to Review

Check operation on one of the three instruments mentioned above.

_{To the reviewer: Make sure to update submodules!}

[davidkeymer]

Pull Requests:
GUI
Release Notes